US Patent Publication No. 2006/0033154, assigned to the assignee of the present application and incorporated by reference, discloses a semiconductor power device having deep source electrodes which can be suitable for a power MOSFET with up to a 300V rating and a lower resistivity drift region. For example, a conventional 100V device may use 1.75 ohm-cm drift region while a device employing deep source electrodes may have a 0.25 ohm-cm drift region.
Conventional MOSFET designs may use a termination structure composed of diffused guard rings to reduce the electric field curvature, but still rely on the drift region to block a significant amount of voltage. If a conventional termination were used on a 100V MOSFET designed with a deep source electrode, the termination would only support about 30V due to the low-resistivity drift region.
Thus, a new termination that is capable of blocking a voltage equal or greater than the active cells of a deep source electrode MOSFET is desired. It is also desired to have a simple process to form the termination when fabricating a deep source electrode MOSFET.